Locking mechanism for jack with elevated platform

ABSTRACT

A locking mechanism for an elevatable lift platform, having a work platform, a scissor-jack and a locking mechanism, is utilized to elevate a chassis for straightening or other repairs. The scissor-jack is contracted by a power actuator, thereby increasing the scissor-jacks&#39; vertical height and elevating the platform. The locking mechanism is comprised of a herringbone lock arm and a lock actuator assembly. The lock assembly is positioned on the power actuator and comprises a two locks, a pneumatic cylinder for extending and contracting the locks vertically, and a lock retainer bar for restricting the extension of the locks. The locks incrementally move along the lock arm horizontally as the jacks are contracted or extended. The locks engage grooves located between teeth on the lock arm that prevent the jacks from contracting or expanding. The locks can disengage the grooves if the pneumatic cylinder is activated to release the locks.

FIELD OF THE INVENTION

[0001] This invention relates to vehicle straightening benches and, more particularly, to a locking mechanism for a vehicle straightening bench with a jack for elevating the bench between different positions.

BACKGROUND OF THE INVENTION

[0002] Occasionally, vehicles are involved in collisions, and before they can reenter meaningful service, the vehicle chassis must be returned, as nearly as possible, to their original configurations. This is frequently accomplished with straightening benches. A typical straightening bench includes a platform for supporting and anchoring a vehicle chassis while forces are applied to the chassis by pulling assemblies. The pulling assemblies utilize hydraulically powered telescoping towers with chains that attach to desired locations on the vehicle chassis.

[0003] Typically, vehicle straightening benches have utilized a jack for elevating the platform. Examples of these vehicle straightening benches include the one disclosed in pending U.S. application Ser. No. 09/973,586, filed Oct. 9, 2001. These vehicle straightening benches use a jack to selectively elevate a platform. The elevatable bench, or lift platform, is suitable for elevating the vehicle chassis, and when combined with anchoring equipment and hydraulic towers, for straightening the chassis. The jack must securely maintain the position of the platform both to protect the chassis and the individuals operating the lift platform, anchoring equipment, and hydraulic pulling towers.

[0004] Safety is a common concern when elevating an object as heavy as a chassis, particularly keeping the object raised while work is performed under and around it. Elevating mechanisms must maintain the raised position not only as gravity pulls the chassis down but also as additional pulling forces of many tons are used to straighten the chassis. If the jack collapses or the chassis shifts under the weight or the pulling forces, the change from an elevated position to a lowered position will be almost immediate. Anyone working around or below an elevated chassis has very little time to react and get out of the way of the collapsing straightening bench or the shifting chassis. Clearly, the consequences of an accident involving such heavy equipment can involve severe injury and potentially death if the jack is not properly secured against unexpected collapses.

BRIEF SUMMARY OF THE INVENTION

[0005] There is, therefore, provided in the practice of the invention a novel locking mechanism, having a lock arm and a lock actuator assembly for operating the lock arm. The actuator assembly includes a lock actuator and a lock, which is operated by the actuator to engage the lock arm.

[0006] In a preferred embodiment, the lock arm includes teeth in a herringbone pattern and the lock actuator assembly has two moveable locks for engaging the teeth of the lock arm. The actuator is a pneumatic cylinder which moves the locks in opposite directions. The locks are supported by a pair of retainer bars, which permit the locks to slide.

[0007] It is further contemplated in the practice of the invention that the locking mechanism is used with a jack, and further in combination with an automotive chassis straightening bench. The bench includes a lift platform, the jack for elevating the lift platform, and the locking mechanism for securing the jack. Preferably, the bench has two jacks with each jack having a locking mechanism.

[0008] In another preferred embodiment, the locking mechanism includes two lock arms and a lock actuator assembly that interact to maintain the jack in an extended or contracted position. The lock arms extend parallel to the lift platform and have rows of teeth on both the upper and lower sides of the lock arm, arranged in a herringbone pattern. The lock actuator assembly includes two locks with end projections shaped to fit between the teeth on the lock arm, a pneumatic cylinder to disengage the lock projections from the lock arm teeth, and two lock retainer bars connecting the two locks and limiting how far apart the pneumatic cylinder pushes the locks.

[0009] Accordingly, it is an object of the present invention to provide an improved locking mechanism for the jack of a straightening bench.

[0010] It is a further object of the present invention to provide an improved vehicle straightening bench with a locking mechanism for selectively securing a jack that elevates automobiles with reduced risk of the straightening bench descending or shifting unexpectedly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] These and other inventive features, advantages, and objects will appear from the following Detailed Description when considered in connection with the accompanying drawings in which similar reference characters denote similar elements throughout the several views and wherein:

[0012]FIG. 1 is a side view of an elevatable platform with a locking mechanism according to the present invention;

[0013]FIG. 2 is a partially exploded perspective view of the locking mechanism of FIG. 1 illustrating a lock actuator assembly, power actuator, and herringbone lock arm;

[0014]FIG. 3 is a side view of the power actuator with the lock actuator assembly exploded therefrom;

[0015]FIG. 4 is a side view of the herringbone lock arm of FIG. 2;

[0016]FIG. 5 is an exploded view of the lock actuator assembly of FIG. 2; and

[0017]FIG. 6 is a rear view of the lock actuator assembly of FIG. 2.

DETAILED DESCRIPTION

[0018] Referring to the drawings in greater detail, FIG. 1 shows vehicle straightening bench 20 constructed in accordance with a preferred embodiment of the present invention. The vehicle straightening bench 20 broadly includes a lift platform 22, two double scissor jacks 24, and two locking mechanisms 26. The jacks 24 selectively contract to elevate the lift platform 22 to a desired height, while the locking mechanisms 26 engage the jacks 24 and maintain the jacks in the desired contracted positions and thus, the lift platform at the desired height.

[0019] The lift platform 22 is generally flat and horizontal, providing the support structure for a vehicle chassis (not shown). The platform supports and anchors the chassis while the jack 24, or a combination of jacks, raise the platform, and while pulling assemblies (not shown) apply straightening forces to the chassis.

[0020] In one embodiment, the jack 24 is a scissor-type jack, similar to those disclosed in U.S. patent application Ser. No. 09/973,586, incorporated herein by reference. As shown in FIG. 1, the jack is on a base 23 positioned between the floor or other support surface and the lift platform 22 to selectively move the platform between a lowered position and elevated positions. This embodiment utilizes two scissor-jacks, one on either side of the lift platform, to elevate the platform, and each jack has two sets of double scissor legs The jacks include a double acting power actuator 32 located between the two sets of scissor-jack legs and below the lift platform 22. The jacks are contracted horizontally by the power actuator 32 to move the platform into an elevated position. Each jack has a locking mechanism, and the jacks and locking mechanisms are substantially identical. Thus, they will generally be described with reference to only one jack and its locking mechanism.

[0021] Referring to FIGS. 2 and 3, the locking mechanism 26 comprises a lock arm 34 and a lock actuator assembly 36. The lock actuator assembly 36 includes a pneumatic lock actuator or cylinder 38, a top lock 60 and a bottom lock 62 connected to the cylinder for engaging the lock arm 34, and a pair of lock retainer bars 42 connected to the locks.

[0022] The lock arm 34, as shown in FIG. 4, is a substantially flat, generally paddle-shaped structure with an upper and a lower perimeter edge. The lock arm 34 has two parallel rows of teeth 48, arranged in a herringbone pattern, running along the upper and lower perimeter edges on the paddle end 50 of the lock arm 34, extending away from the lock actuator assembly 36. The teeth 48 extend outwardly from the perimeter edges of the lock arm, with an equal number of teeth on each side. The teeth of the top and bottom rows of teeth are arranged so that each upper tooth is aligned with a lower tooth and every tooth is equally spaced apart. Each tooth has a straight back side 43 and a sloping front side 45. The back side 43 forms approximately a 90° angle with the perimeter of the lock arm 34. The front side slopes toward the perimeter of the lock arm, forming approximately a 135° angle with the perimeter. The teeth define grooves 46 along the perimeter of the lock arm. The angle of the slope may be varied as long as the top and bottom locks 60, 62 are able to move smoothly along the slope of the tooth when extending the jack 24. The teeth are substantially flat on top, 47 and the rows of teeth terminate at a rectangular stop 33.

[0023] The lock arm 34 is toothless on the handle end 52, farthest from the lock actuator assembly 36, as illustrated in FIG. 2. The toothless handle end 52 begins narrowing with concave curves where the paddle end 50 starts. The handle end 52 terminates in a rounded shape, with an aperture 54 in the middle of the circular handle end for attaching to a pivot point A on the jack and the power actuator 32, as illustrated in FIGS. 1 and 2. The handle end is attached by a pivot rod 55 to the jack at pivot point A where two of the bars comprising the jack cross to form an X. The pivot rod also extends through a cylindrical pivot tube 53 attached to the end of the actuator 32. The pivot tube 53 has two support blocks 49 extending downward below the level of the power actuator 32. The lock arm 34 has a slot 56 extending centrally along the length of the lock arm 34 and in the middle of the paddle end. A different X portion of the scissor-jack 24 is attached to the paddle end by a sliding pivot rod 90 at a sliding pivot point B on the jack 24 through the slot 56 in the paddle end and to a lock assembly axle receiver 57, which is formed with a mounting block 59 attached to the end of the power actuator 32 opposite the pivot tube 53. The slot 56 allows pivot point B to move horizontally in relation to the lock arm 34, as the jack is extended and contracted.

[0024] The lock actuator assembly 36, as shown in FIGS. 3, 5 and 6, comprises the pneumatic cylinder 38, top lock 60, bottom lock 62, two lock retainer bars 42 and the mounting block 59. The top and bottom designation are intended for use in distinguishing the components and are not intended to be limiting. Thus the locks may be in any relative orientation. The pneumatic cylinder 38 is preferably a single acting pneumatic cylinder but can be double acting. Extending from the bottom of the pneumatic cylinder is a bottom bracket 66 for connecting the pneumatic cylinder to the bottom lock 62. Extending from the top of the pneumatic cylinder is a cap bracket 68 for connecting the pneumatic cylinder to the top lock 60. The lock actuator assembly 36 is positioned on the end of the power actuator 32 by the mounting block 59, as shown in FIGS. 2 and 3.

[0025] Referring to FIGS. 2, 5, and 6, the top and bottom locks 60, 62 engage the teeth 48 of the lock arms 34 to hold the jack 24 in a certain position. The top and bottom locks 60, 62 are substantially identical and the following description of the bottom lock 62 applies to the top lock 60 as well. The lock 62 is generally rectangular in shape. The two ends of the lock 62 have outwardly extending projections 70 formed as part of the lock, which resemble the shape of the teeth on the lock arm 34. The lock end projections 70 actually engage the teeth 48 of the lock arm 34 and inhibit a reverse motion of the jack 24 when elevating the lift platform 22. The lock end projections 70 have a flat top 73 parallel to the lock 62, and a flat face 77. The flat top is slightly more narrow than the groove 46 between two teeth on the lock arm 34. The flat top 73 of the projection 70 terminates in a slight tapering shoulder 72 on its back end and an extended tapering shoulder 74 on its front end.

[0026] The lock 62 also has two leg projections 76 extending from the top of the lock. These projections 76 begin on either side of the lock immediately inside of the end projections 70. The leg projections 76 are generally square in shape when viewed from the top. The leg projections 76 each have a slide slot 78 extending all the way through the lock. The slide slots 78 are for receiving shoulder bolts 86 that will connect the lock retainer bars 42 to the lock 62 and the mounting block 59.

[0027] The lock 62 also defines an oval-shaped recess 80 between the top projections 76. The recess 80 is for receiving the bottom bracket 66 of the pneumatic cylinder 38. The recess 80 has six apertures, three on each side. Each aperture is directly across from an other to form three pairs of apertures. The middle pair of apertures 82 are for receiving a grooved clevis pin 84 with retaining ring 85. On the bottom lock 62, the clevis pin 84 connects the bottom bracket 66 of the pneumatic cylinder 38 to the lock. On the top lock 60, the second clevis pin 84 connects the cap bracket 68 to the lock. Spacers 87 are positioned on either side of the brackets 66, 68 to center the cylinder 38 and keep it from tilting. The clevis pins 84 pass through the spacers 87.

[0028] The remaining spring apertures 83 in the lock's central recess 80 are for attaching tension springs 81 (only three shown) to the locks 60, 62. The springs, which serve as biasing members, extend from the top lock 60 to the bottom lock 62, attaching to the similarly situated apertures on each lock. The tension springs are biased to keep the locks 60, 62 together in the locked position/engaged position. Four springs 81 will connect the top lock to the bottom lock in a preferred embodiment. The top lock 60 is also biased into engagement with the teeth of the lock arm 34 by gravity. Conversely, the bottom lock 62 is biased out of engagement with the teeth of the lock arm 34 by gravity. The clevis pins 84 and brackets 66, 68, along with the springs, allow the locks 60, 62 to tilt relative to each other as they slide over the teeth 48. Further, the locks can move independently of each other.

[0029] The lock retainer bars 42 are substantially identical and will be described by referencing only one. The bar 42 is a thin rectangular structure with two apertures 44 near both ends of the retainer. The retainer bar is mostly smooth, with the exception of the two apertures. The aperture 44 is counter bored to receive the shoulder bolt 86 that attaches the retainer bar to the top and bottom locks 60, 62 and the mounting block 59. A preferred embodiment has two retainer bars that allow the locks to slide over the teeth 48 of the lock arm 34, one connecting each end of the top and bottom locks. The retainer bars 42 are positioned on the outer side of the locks, and the four shoulder bolts extend through the apertures 44, through the slide slits 78, and attach to the mounting block 59. Thus, the bars 42 are fixed relative to the mounting block 59 and actuator 32, and the locks 60, 62 are able to slide between the block 59 and bars 42.

[0030] The mounting block 59 is substantially rectangular in shape with a large aperture 57 for receiving the slide pivot rod 90 and small apertures 61 for mounting the lock actuator assembly 36. The bottom of the mounting block 59 extends below the power actuator 32. The mounting block supports the weight of the power actuator 32 and lock actuator assembly 36 when the lift platform 22 is completely lowered. The mounting block 59 and support blocks 49 both rest on the floor when the bench is fully lowered, supporting the power actuator 32 and lock actuator assembly 36.

[0031] The vehicle straightening bench 20 according to the present invention provides a secure mechanism for extending and contracting the jacks 24 when lowering or elevating the platform 22. The locking mechanism 26 prevents the jacks 24 from extending or contracting too quickly or unexpectedly when changing the height of the platform. The locking mechanism also secures the jacks at a chosen position to maintain the height of the platform.

[0032] When one desires to elevate the lift platform 22, the power actuator 32 is activated to contract the scissor-jacks 24. The activity of the power actuator 32 brings point A on the jacks closer to point B on the jacks, thereby increasing the vertical height of the jacks and raising the platform 22. As the jacks 24 are contracted, the locking mechanism 26 is left in a passive state. The horizontal movement of point B closer to point A changes the position of the lock actuator assembly 36 relative to the lock arm 34. The lock actuator assembly 36 moves closer to point A because it is positioned on the end of the power actuator 32 at Point B.

[0033] As the jacks raise the platform, the locks 60, 62 of the lock actuator assembly 36 begin sliding from one tooth 48 on the lock arm 34 to another, steadily moving closer to point A. The extended tapering shoulder 74 of the sloped end projections 70 of each lock 60, 62 slide along the sloped side 45 of each tooth as the lift platform is raised substantially lifting the locks out of the grooves while the springs sequentially pull the locks into the next grooves. As the power actuator 32 and the jacks 24 continue to contract, the locks 60, 62 continue to move up the sloped side of each successive tooth 48, until it clears the top of the tooth and is pulled into the next groove 46 between teeth by the springs. During this operation, the pneumatic lock cylinder 38 is either left at rest, so that the force of the lift actuator 32 overcomes the bias of the springs 81 as the locks slide over the teeth, or alternately the lock cylinder is extended allowing the locks to simply pass over the teeth.

[0034] Once the platform 22 reaches the desired height, the power actuator 32 stops contracting, thereby halting the contraction of the jacks 24. Once the jacks stop contracting, the pneumatic cylinder 38 and springs also stop extending, allowing the locks 60, 62 to move toward each other and to settle into the grooves 46 of the lock arm 34 so that the backside 43 engages the flat face 77 of the locks to hold the relative position between the pivot points A & B. The locks will hold the jacks in the desired position because they cannot be moved to a different groove without activation of the power actuator 32 and the pneumatic cylinder 38. The locking mechanism 26 prevents the downward force of the chassis from compacting the jacks vertically and pushing them apart horizontally. When one desires to lower the lift platform 22, the pneumatic cylinder 38 is activated to release the locks 60, 62 from their positions in the lock arm grooves 46. The pneumatic cylinder 38 expands vertically to push the locks out of the grooves into a disengaged position. At the same time, the power actuator 32 is activated to extend the jacks, moving point B away from point A. The platform is lowered as the jacks expand horizontally. The pneumatic cylinder 38 keeps the locks apart as the lift platform 22 is lowered, preventing the end projections of locks from engaging the grooves of the lock arm 34, as the power actuator 32 moves the lock actuator assembly 36 closer to the end of the lock arm 34.

[0035] When an operator wishes to raise the straightening bench as described in a preferred embodiment, the operator will follow the method outlined below. The operator first activates the power actuator 32 to begin contracting the jacks 24 and raising the lift platform 22. When the lift platform reaches the height desired by the operator, the power actuator is deactivated. If the operator wishes to lower the platform, the locking mechanism must first be activated. The power actuator must be activated to raise the platform slightly. Then, with the locking mechanism still powered to move the locks away from each other and keep the locks apart, the power actuator is activated to lower the platform. When the platform has descended to the desired position, the power actuator is deactivated. The locking mechanism is then deactivated, allowing the locks to engage the grooves of the lock arm.

[0036] Thus, an elevateable lift with locking mechanism 26 is disclosed which utilizes a lock arm 34 and top and bottom locks 60, 62, powered by a pneumatic cylinder 38 to incrementally control a jack 24 for elevating a lift platform 22. This invention allows for greater stability of the jack during the elevation and lowering of the platform. While preferred embodiments and particular applications of this invention have been shown and described, it is apparent to those skilled in the art that many other modifications and applications of this invention are possible without departing from the inventive concepts herein. It is, therefore, to be understood that, within the scope of the appended claims, this invention may be practiced otherwise than as specifically described, and the invention is not to be restricted except in the spirit of the appended claims. Though some of the features of the invention may be claimed in dependency, each feature has merit if used independently. 

What is claimed is:
 1. A locking mechanism for a jack comprising: a lock arm; a lock actuator assembly, comprising: a lock actuator cylinder; at least one lock connected to the lock cylinder; and at least one lock retainer bar connected to the lock.
 2. The locking mechanism according to claim 1 wherein the lock arm further comprises an elongated body with at least one row of teeth extending from the outer perimeter of the lock arm.
 3. The locking mechanism according to claim 2 wherein the backside of each tooth on the lock arm forms approximately a 90° angle with the lock arm and the front side of each tooth slopes at approximately a 45° angle to the lock arm.
 4. The locking mechanism according to claim 3 wherein the lock arm is a herringbone lock arm with two rows of substantially equally spaced teeth on the upper and lower perimeter, each tooth on the upper perimeter aligned with a tooth on the lower perimeter.
 5. The locking mechanism according to claim 4, wherein the lock arm further comprises an aperture in one end of the lock arm for connecting the lock arm to the scissor-jack by a pivot rod.
 6. The locking mechanism according to claim 5, wherein the lock arm further comprises an elongated aperture for connecting the lock arm to the jack.
 7. The locking mechanism according to claim 1, wherein the lock actuator assembly further comprises at least one spring extending between the locks.
 8. The locking mechanism according to claim 6, wherein the lock further comprises a projection for engaging the lock arm.
 9. The locking mechanism according to claim 7, wherein the lock further comprises at least two slots for connecting the lock to the lock bar retainer.
 10. The locking mechanism according to claim 8, wherein the lock further comprises a recessed center for receiving the pneumatic cylinder.
 11. The locking mechanism according to claim 9, wherein the lock further comprises at least one aperture for connecting the pneumatic cylinder to the lock.
 12. The locking mechanism according to claim 10, wherein the lock further comprises at least one aperture for connecting the spring to the lock.
 13. A jack comprising: a scissor-type jack; a power actuator for contracting and expanding the scissor-jack; a locking mechanism for securing the jack in position; at least one lock arm; and a lock actuator assembly, including: a lock for engaging the lock arm including a plurality of teeth; and a pneumatic cylinder for operating the lock.
 14. The jack according to claim 13, wherein the lock actuator assembly is positioned on the power actuator.
 15. The jack according to claim 14, wherein the lock actuator assembly further comprises two locks and a spring extending between the two locks, operable to bias the locks towards each other in an engaged position relative to the teeth of the lock arm.
 16. The jack according to claim 13, wherein the lock arm comprises two rows of teeth projecting out from the perimeter of the lock arm.
 17. The jack according to claim 13, wherein the lock comprises at least one projection shaped to fit between the teeth of the lock arm.
 18. A straightening bench for selectively elevating a chassis, said bench comprising: a platform; a plurality of jacks for elevating the platform; a power actuator for extending the jacks; a locking mechanism for selectively securing the jacks; a lock arm including a plurality of teeth extending from the perimeter of the lock arm; and a lock actuator assembly, comprising: at least one lock connected to the pneumatic cylinder operable to selectively engage the teeth of the lock arm; and a pneumatic cylinder operable to move the lock between engaged and disengaged positions relative to the lock arm teeth.
 19. The bench according to claim 18, wherein the lock arm further comprises a plurality of teeth equally spaced along the upper and lower perimeter of the lock arm, each upper tooth spaced symmetrically with a lower tooth.
 20. The bench according to claim 18, wherein the lock further comprises at least one projection shaped to fit between the teeth of the lock arm.
 21. A locking mechanism for a jack for raising and lowering a vehicle straightening bench, the mechanism comprising: a lock arm including a plurality of teeth; a lock actuator assembly, including: a lock operable to selectively engage the teeth; and a lock actuator operable to move the lock between engaged and disengaged positions relative to the teeth.
 22. The mechanism according to claim 21, wherein the teeth comprise a top row of teeth and a bottom row of teeth, the lock actuator assembly further includes a bottom lock, the lock comprises a top lock, and the lock actuator is operable to move the top and bottom lock between the engaged and disengaged positions relative to the top and bottom rows of teeth.
 23. The mechanism according to claim 22 wherein the lock actuator assembly further includes a biasing member biasing the top and bottom locks toward each other into the engaged position.
 24. The mechanism according to claim 22 wherein the lock actuator is positioned between the top and bottom locks and is operable to move the locks forward away from each other into the disengaged position.
 25. The mechanism according to claim 21 wherein the lock arm includes an aperture for attachment to a first pivot point of the jack and an elongated aperture for slidably receiving a second pivot point of the jack. 